Lessons and Experiences with High-Level Synthesis

Editor's note:This article is a designer's perspective on the benefits and challenges of using commercially available HLS tools. The authors have used three such tools for synthesizing industrial ASICs. They discuss their impact on four criteria: design goals, verification closure, ECO handling, and productivity gains.—Philippe Coussy, Université de Bretagne Sud     

Bivariate Quasi-Steady Model for Prediction of Roof Corner Pressures

Extremely high-suction pressures generated beneath the conical vortex flow in the roof-corner region have a devastating effect on the building roofs in high-wind events. The application of quasi-steady theory near the roof corners of low-rise buildings deserves careful investigation for the appropriate assessment of the design wind loads. A synchronized incident wind and pressure data acquisition system was set up on the full-scale experimental building at Texas Tech Univ. Experiments were conducted systematically to simultaneously collect the incident wind and roof-corner pressure data under the influence of cornering winds. By using a conditional sampling technique, a bivariate quasi-steady model was established to incorporate the influence of both horizontal and vertical wind directional variations on the roof-corner pressures. Comparison between the measured pressures and the model-predicted pressures has shown that the quasi-steady theory in the suggested form is applicable in the roof-corner separated flow region where vortices are present. This conclusion further justifies the application and codification of quasi-steady approach for wind load assessment of low-rise buildings and other structures.     

Analytic representation of dynamical systems using pseudo-inverse methods

Summary The term `analytic representation' in configuration space is often used for the representation of a physical system in terms of Lagrangians and/or Lagrange's equations. Such representations play a role in the methodological formulation for a wide variety of physical problems. We deal with two different approaches to construct Lagrangians for a number of equations. Examples cited cover both point and continuum mechanics. This work will be of special significance to those who would like to study problems of contemporary physics without being directly involved in the rigorous theory of Helmholtz for inverse variational problems. The first procedure chosen by us depends on the method of characteristics as used for solving first order partial differential equations while the second one exploits the symmetries of the Lagrangian and the equation of motion. For simple cases, both approaches are applicable without any modification. However, in more realistic situations the methods need to be supplemented by some ansatz.     

An ROI-Based strategy for implementation of existing and emergingtechnologies in helicopter manufacturing

An aircraft structure has several part families. These part families are currently manufactured using a baseline technology. There are several other competing technologies, already existing or still in the development stages, that could be applied to the structure under consideration. Each technology has a probability distribution of costs and savings (over baseline) associated with it. The problem is to determine which of the candidate technologies should be used and to what extent, to manufacture different part families. In this paper, the authors have obtained the optimum time-dependent technology mix over a finite planning horizon, such that the return on investment (ROI) is maximized. This has been done subject to the constraints that the risk resulting from investment in a combination of technologies, does not exceed, in any year, some predefined quantity, and that the quantity produced using a particular technology does not exceed its applicability in any year     

RF MEMS waveguide switch

This paper presents a novel concept for an RF microelectromechanical systems (MEMS) waveguide switch. The proposed switch employs a ridge waveguide integrated with MEMS rotary actuators based on a thermal plastic deformation approach. The switch promises to be useful in high-power applications, as well as in millimeter-wave applications. Two switch implementations are presented: one with a waveguide interface and the other with a coplanar-waveguide interface for wide-band applications. Electromagnetic simulation results are presented showing the ultimate potential of the proposed concept. Both switch implementations have been fabricated and tested. The achievable measured results are very encouraging and demonstrate the feasibility of such novel types of MEMS switches. The power-handling capability of the switch is also investigated both theoretically and experimentally.     

Static analysis of arbitrarily shaped conducting and dielectricstructures

In this paper, a simple and efficient numerical procedure is presented to compute the charge distribution and capacitance of conducting bodies in the presence of dielectric structures of arbitrary shape and finite size. The method presented is robust and provides accurate results for both low as well as high dielectric-constant materials as supported by numerical examples     

A framework for optimal battery management for wireless nodes

The focus of this paper is to extend the lifetime of a battery powered node in wireless context. The lifetime of a battery depends on both the manner of discharge and the transmission power requirements. We present a framework for computing the optimal discharge strategy which maximizes the lifetime of a node by exploiting the battery characteristics and adapting to the varying power requirements for wireless operations. The complexity of the optimal computation is linear in the number of system states. However, since the number of states can be large, the optimal strategy can only be computed offline and executed via a table lookup. We present a simple discharge strategy which can be executed online without any table lookup and attains near maximum lifetime.     

3-D-integrated RF and millimeter-wave functions and modules using liquid crystal polymer (LCP) system-on-package technology

Electronics packaging evolution involves system, technology, and material considerations. In this paper, we present a novel three-dimensional (3-D) integration approach for system-on-package (SOP)-based solutions for wireless communication applications. This concept is proposed for the 3-D integration of RF and millimeter (mm) wave embedded functions in front-end modules by means of stacking substrates using liquid crystal polymer (LCP) multilayer and /spl mu/BGA technologies. Characterization and modeling of high-Q RF inductors using LCP is described. A single-input-single-output (SISO) dual-band filter operating at ISM 2.4-2.5 GHz and UNII 5.15-5.85 GHz frequency bands, two dual-polarization 2/spl times/1 antenna arrays operating at 14 and 35 GHz, and a WLAN IEEE 802.11a-compliant compact module (volume of 75/spl times/35/spl times/0.2 mm/sup 3/) have been fabricated on LCP substrate, showing the great potential of the SOP approach for 3-D-integrated RF and mm wave functions and modules.     

Fluid Flow and Heat Transfer in Air Jet Impingement in Food Processing

ABSTRACT: Air impingement technology is gaining popularity in food-processing operations such as baking, freezing, drying, and toasting. In this article, physical characteristics of impinging jets, such as turbulent mixing in the free jet region, stagnation, boundary-layer formation, recirculation, and their interactions with food products in terms of heat and mass transfer have been reviewed. The discussion includes experimental methods used for measurement of heat and mass transfer for single and multiple slot and circular jets. Procedures used for measurement of heat-transfer coefficient such as lumped sensor method, micro-calorimetric approach, and use of flux sensors are presented. Typical qualitative and quantitative flow-field studies using planar visualization and laser Doppler anemometry have been reviewed. Numerical modeling of air impingement systems is discussed with special consideration of problems arising in food-processing systems.     

Multitransfused children with thalassemia major do not have gallstones

A case of oral non-Hodgkin's lymphoma as the first manifestation of AIDS is described. The clinical presentation was that of a periodontal lesion and mental nerve paraesthesia, which may have lead to initial confusion in diagnosis and management.